Flashcards in Industrial toolkit 2 Deck (41):
Non-thermal processes include?
irradiation, Pulsed electric fields and high hydrostatic pressure
Bacteriaiophage as a processing aid.. a little bit about them.
tip: considered organic
most abundant organisms
- very specific target
NO impact on food quality (not spoilage organism!)
use 10^8 PFU = 3 log kill.
- Phage must contact bacterial cell
- dependent on food.
What is bacteriophages used to control in RTE meats?
Used especially in microwaves to excite water molecule to heat up food.
high energy, shorter wavelength
Power source is cavity magnetron which dielectric heating and oscillation of water molecules.
Microwaves as thermal treatment
pro's: rapid, borad spectrum of actvity (viruses, mold, yeast, bacteria)
con: thermoydnaimic gradients ( distribution of water not always uniform), dependent on Aw, endospores not killed.
Ultraviolet Radiation ( non-ionizing)
Power source: UV lamp
DNA absorbs UV.
causes DNA damage,
Affect depends on intensity and time.
What is resistant to UV radiation?
Gram negative< gram positive and yeast < endospores < mold spores <<<< viruses
The ability of these to recover is reverse.
What is hte pro and con of UV radiation?
Con:limited penetration (smooth surface), and pro is surfaces of foods and clear juices.
Ionizing radiation what is it?
Ejecting e- out of compound ( removes e- from atom to form ions)
- Distribution of atomic nucleus requred to be radioactive.
Uses x-rays, gamma rays, beta-particles
high frequency, high energy radiation
what is the positives of using ionizing radiation?
Control and near-sterility of bacteria, yeasts, moulds, endospores and viruses.
What are the three forms of ionizing radiation used?
B-particles, x-rays, gamma rays
High energy e-, stream of electrons emitted, little control on dosage, and some concern about radioactive food.
produced from high voltage equiptment
Describe gamma rays
radioactive source C0^60 or Cs^137,
Cheapest form, uses atomic waste product, dispoal issues and can use electron beam accelerators.
Three forms of processes of ionization radiation.
Lose dose, considered soft pastuerization, QUALITY enhancement, and reduces spoilage orgnisms
Equivalent to pasteurixation, specifically refers to REDUCTION of pathogens.
Equivalent to sterilization, much higher dose, and not applied to food ( everything dead!)
Cons of ionizing radiation
consumer resistance--> radioactive food.
dispoal of radioiostopes, SIDE EFFECTS: lipid oxidation (rancidity) (as increase dose, increase problem).
- Some food can be frozen prior to irradiation to inhibit sensory property changes.
What doses of irradiation do you use on fresh foods vs. frozen?
frozen: 2-7 kGy
What is cold pasteurization?
Use electron beam. (same outcome as gamma irradiation)
- limited ability to penetrate surface.
3.5cm in water, and products such as meat must be thin.
Cold pasteurization effects on microorganisms
Product and dose dependent.
3 -6 log reudcition in E. coli O157:H7 in beef.
Reduction of other pathogens.
Salmonella spp., Yersinia enterocolitica, Campylobacter.
LITTLE IMPACT on spore-forming bacteria.
Reduction in public health costs associated with foodborne diseases.
- Decrease cost in waste reduction and lawyers.
extends storage life.
Written statement requ9ired and international symbrol required.
PEF Pulse Electric Field technology
Apply current. (short, high-voltage purses of electricty) that causes cellular distribution.
Maintains aroma, taste and apperance.
PEF processing applications
Microbial inactivation, enhance dryng and brining injection (reduces Aw)
How does PEF work?
High voltage--> breaks cell membranes.
expand existing pores (form new pores too) Cells become permeable to small molecules which causes swelling and rupture= death.
Is pore formation reversible?
Sometimes. Depends on:
1. Electric field intensity
2. Pulse duration and frequency
3. Conductivity of samples ( Aw, ionic strength, pH)
Microorganisms vulnerable to PEF?
Metabolically active membranes ( water on both sides to facilitate ion movement)
- bacteria, molds, yeasts
Not so affective on spores and virsuses. Hurdles present.
Advantage of PEF?
Keeps product quality
uniform, no gradients of voltage within a product,
heating enhances antimicrobial affects.
Pore-forming compounds enhance antimicrobial affects.
Disadvantages of PEF?
Membranes, low Aw has protective effect.
Liquid to semi-luid foods (meat, eggs, juices, milk, soup),
Anything with a high Aw can be used though.
HHP or high hydrostatic pressure
Add pressure. Compression of a substance.
Achieve favorable thermodynamic changes.
HPP processing applications
Increase food quality
- microbial inactivation
- texture and protein modification
- phase transitions
HPP alters thermodynamic properties unlike PEF.
HHP in foods
Compression of molecule will heat it up. it is a non-thermal process though.
- Used in cheese production, jam.
How does HHP work?
Compression of a sample (decrease volume) Causes heating (adiabatic heating)
molecular rearragement and folding occurs.
- dissociation reactions occur,
- water very important. (small crystal- less destruction.)
What pressure stops growth?
Usuually around 50MPa's.
Protein denaturation in pressure and heat
heat: Increae heat, new covalent bonds form, protein denature and it's cheap.
Pressure: no new covalent bonds, expensive, rearrangement of molecules dissociation of proteins. loss of protein secondary, and irrversible protein denaturation.
Microorganisms vulnerable to HHP
Vegetative bacteria, fungal and mold spores, and viruses.
Bacterial endospores : C. spp and Bacillus spp.
Advantages of HHP?
Maintain quality of product, low energy vost vs. heat,
Heat enhances effect,